/Engine/Source/Editor/StaticMeshEditor/Public/IStaticMeshEditor.h
Store the custom data using the key. Remark: The custom data memory should be clear when the editor is close by the user, this is not persistent data. Currently we use it to store the state of the editor UI to restore it properly when a refresh happen.
virtual void SetCustomData ( const int32 Key, const int32 CustomData )